const s = new Set();

[2, 3, 5, 4, 5, 2, 2].forEach(x => s.add(x));

for (let i of s) {
    console.log(i);
}

const set = new Set([1, 2, 3, 4, 5, 5, 5, 5, 5]);
console.log([...set]);  // [ 1, 2, 3, 4, 5 ]

const items = new Set([1, 2, 3, 4, 5, 5, 5, 5, 5]);
console.log(items.size);  // 5